1. Field of the Invention:
The present invention relates to a molding member for an automobile window plate, with a longitudinally variable cross-section.
2. Description of the Related Art:
An automobile generally employs various kinds of window molding members which extend along the periphery of a front or rear window plate, i.e. along a pair of front or rear pillars and the front or rear edge of the roof panel of the automobile body. A variety of requirements have been imposed on such molding members mainly from design and/or functional viewpoint, resulting in an increased demand in the automobile industry for the window molding members whose cross-sectional shape varies in the longitudinal direction.
Specifically, there has been proposed a window molding member having an upper portion of a first predetermined cross-section, a side portion of a second predetermined cross-section, and a corner portion arranged between the side and upper portions, where the cross-section changes gradually from the first to the second. When the molding member is arranged along the periphery of a front window plate, the first cross-section of the upper portion contributes to realize a so-called flush outer surface of the automobile body, while the second cross-section of the side portion serves to define a weir along the side edge of the window plate. During driving in rainy conditions, the weir serves to prevent rain water on the window plate from flowing across the side portion of the molding member toward the side window, thereby effectively preserving the driver's and/or navigator's sight through the side windows.
For producing a window molding member with longitudinally variable cross-section, various methods are known. A typical method is to physically divide each molding member into first and second extruded portions with the respectively predetermined cross-sectional shapes, which are connected with each other either by an injection molding process or by using a separate corner connection-piece. However, connection of these two portions by means of the injection molding accompanies formation of undesirable burrs along the junctions and resultant deterioration in the appearance, while use of the corner connection-piece results in increased number of the required components and assembly steps.
These problems can be more or less overcome by a method disclosed e.g. in U.S. Pat. Nos. 4,757,659 and 4,757,660 to Miyakawa et al., which includes extrusion of a continuous elongate preform body with a constant cross-section throughout the entire length. In this case, the preform body portion forming the upper portion of the molding member is subjected to cutting at the base end of a first arm section and at an area of a leg section from where a second arm section extends, to allow removal of these arm sections from the relevant body portion, and provide the upper portion with a glass plate receiving groove between the top and third arm section. On the other hand, the preform body portion forming the side portion of the molding member is subjected to cutting at the base end of the third arm section, to allow removal of that arm section from the relevant body portion, and provide the molding side portion with another glass plate receiving groove between the first and second arm sections.
Such a method is still disadvantageous in that the molding member cannot be produced accurately and efficiently, due mainly to the above-mentioned local cutting of the arm sections to form two glass plate receiving grooves along the upper and side portions of the molding member, respectively. Moreover, there are substantial difficulties in securing the molding member to the periphery of the glass plate as well, since the first arm section along the corner portion between the upper and side portions has to be formed with a receiving groove into which the glass plate must be carefully inserted, requiring delicate and time-consuming manual operations.